The present invention relates to a tubular reinforcement element between a hollow tubular member and another member, and also to a method of making such tubular elements. The invention is particularly applicable for reinforcing the connection of two hollow tubular members, such as in constructing the tubular frame of a bicycle, and is therefore described below with respect to this application, but it will be appreciated that the invention could advantageously be used in many other applications as well.
A common technique for joining together two hollow tubular members, such as in the construction of bicycle frames, is to use an external lug which includes a sleeve enclosing and bonded to the outer surface of one tubular member and formed with a peripheral flange bonded to the outer of the other tubular member. The bonding of the external lug may be effected by welding or by brazing. While such a tubular joint construction provides relatively high mechanical strength, it is visible and may therefore detract from its external appearance. Moreover, it is expensive to produce.
German Patent 94,366 describes a method of connecting two tubular sections of bicycle frames. The reinforcement member is an investment casting which is expensive to manufacture.
U.K. Patent 421,687 relates to seat lugs for cycles, which are a standard common fully symmetrical draw cup with a flat bottom with or without the optional tabs which are obtained by cutting slots in the side wall of said lug.